From: Thomas Schilling <nominolo@googlemail.com>
Date: Mon, 24 Aug 2009 18:22:52 +0000 (+0000)
Subject: Make FastString thread-safe.
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=738f70785e381ca2f43413a1d8efa4d5929b8231;hp=738f70785e381ca2f43413a1d8efa4d5929b8231;p=ghc-hetmet.git

Make FastString thread-safe.

This is needed both for per-session parallelism and for allowing
multiple concurrent sessions in the same process.  With the help of
atomicModifyIORef and unsafePerformIO it is also quite fast--an MVar
would most likely be slower.  On a full compilation of Cabal's head
branch it was about 1-2 percent slower, but then overall compilation
times varied by about 4 percent, so I think it's worth it.
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